I think he would be perfect!
I think he does way better in comedies than in action movies, and he has a real interest in the character and seeing the movie (if there were to ever be one) done right and stick to the source material

The Green Lantern movie was ruined by being written poorly, just like Origins: Wolverine. The only other actor I can think of to play Deadpool would be Charlie Day, and he'd have to get into some serious shape.